Linux CLI – navigation

Linux organizes its files in what is called “hierarchical directory structure”. This means they are organized in a tree like structure consisting of directories (folders) and files. Each directory can contain files and other directories. The first directory in the file system is called “root directory”. Unlike Windows, Linux always has a single root directory, no matter how many drives or storage devices are attached to the computer.

When you first open your terminal you will arrive at home directory. Each user has his own home directory. Let’s take a look how you can move up and down the file system tree.

pwd

To check where are you at any given moment you can print current working directory.

$ pwd
output: /root/home/christopher

cd

To navigate through the file system tree, you can use change directory command followed by the relative or absolute path to another directory. Relative path starts from your current working directory while absolute path starts from the root directory. You can recognize absolute path by the leading slash in the path name.

“.” – Refers to your current working directory
“..” – Refers to the parent directory of your current working directory

Examples

absolute path

$ cd /usr/bin

relative path

$ cd my-projects$ cd ./my-projects

go to parent directory of your current working directory

$ cd ..

go back to previous directory

$ cd -

go to home directory

$ cd $ cd ~

go to user’s ( bob ) home directory

$ cd ~bob

ls

You can check out the contents of any given directory with list command followed by the path to the directory. If no path is specified contents of current working directory will be listed.

Flag short	Flag Long	Description
-a	–all	Display all files, even those with names that begin with a period
-A	–almost-all	like the `-a` option but doesn’t display `.` and `..`
-d	–directory	use this in conjunction with `-l` to see details of the directory itself rather than its contents
-l		Display results in long format
-F	–classify	append “/” to directory names
-h	–human-readable	In long format listing, display file sizes in human readable format rather than in bytes
-r	–reverse	Display results in reverse order. Normally results are displayed alphabetically
-S		Sort by file size
-t		Sort by modification time

Examples

List contents of home directory and current working directory

$ ls ~ .
 >>> -rw-rw-r--   1 root root   4096 feb 15 15:46 index.html

Let’s take a look on the ls -l output

code	explaination
-rw-rw-r	access rights to the file
1	number of files hard links
root	username of the files’s owner
4096	file size in bytes
feb 15 15:46	date of last modification
index.html	file name

file

In Linux file name is not required to reflect its content. This means it’s normal for a file to not have an extension. To find out what kind of file we are dealing with we can use file command.

$ file favicon
>>> ./favicon PNG image data, 185 x 220, 8-bit/color RGBA, non-interlaced

less

Less is a program and a command for viewing text files.

command	action
`PAGE UP` or `b`	scroll one page up
`PAGE DOWN` or `SPACE`	scroll one page down
`G`	move to the end of the file
`1G` or `g`	move to the beginning of the file
`/searchphrase`	find new occurrence of searchphrase
`n`	find next occurrence of previous search
`h`	display help
`q`	quit less

Example

$ less /etc/passwd